The genus Shigella has been one of the most common causes of diarrhea in underdeveloped countries, being responsible for the mortality rate and morbidity in high risk populations such as children under five and the elderly. The aim of this study, developed at the Evandro Chagas Institute, Pará, Brazil, from 1979 to 2009, was to evaluate the frequency of species and serotypes of 122 isolates of Shigella spp. isolated from patients with acute diarrhea. The isolates were identified by bacterial culture media with selective indicators and biochemical tests, and serogroups and serotypes were determined by the slide agglutination test. The serogroups most frequently found were S. flexneri (66.4%) and S. sonnei (32.8%). The serotype 2a of S. flexneri was the most frequent (54.3%) followed by 1b (17.2%). Most patients were aged between 0-5 years (44.6%), of which 38.2% cases had S. flexneri and 47.5% S. sonnei. Patients older than 18 years accounted for 39.2% of infections, with 37.0% S. flexneri cases, 32.5% S. sonnei, and 100% S. boydii. These results emphasize the need for continuous surveillance in the State of Pará.